Magnetic clutch



1952 M. P. WINTHER MAGNETIC CLUTCH Filed Dec. 13, 1949 Patented Aug. 5, 1952 UNITED STATES PATENT OFFICE MAGNETIC CLUTCH Martin P. Winther, Gates Mills, Ohio, assignor to Martin P. Winther, as trustee Application December 13, 1949, Serial No. 132,764

'ZClaims.

This invention relates to magnetic clutches, and more particularly, to compound servoactuated magnetic friction clutches and to clutch facings therefor.

Briefly, the invention is incorporated in a disc type, friction clutch having relatively rotary driving and driven clutch members. A compound or double clutch arrangement is shown but some phases of the invention are applicable to single clutch arrangements. One of the clutch members of each of the double clutches comprises a pair of pressure elements, at least one of the pressure elements being axially movable by magnetic attraction toward the other. The other rotary member .of the clutch comprises an interposed clutch plate provided with clutch linings or facings. The clutch linings are of two types; first a magnetic type which may have characteristics of relatively low wear-resistance and frictional-coefficient, and; second a non-magnetic type having characteristics of relatively high Wear-resistance and frictional-coefficient. A toroidal magnetic circuit is provided by an annular field coil so as to interlink both pressure elements, the magnetic field passing between the pressure elements and through the plate and clutch lining in areas having the magnetic clutch linings. Other areas of the clutch faces are provided with the clutchlinings having wear-resistant high-friction properties. These wear-resistant linings are particularly adapted to resist wear, stress and strain caused by servo-action wedge closure operators, such servo-action being 7 preferably incorporated in the clutch. The servo closure operators are-arranged andmounted so as to provide improved servo-action and simplicity of construction. In the compound or double clutch arrangementthe electromagnetic circuits which will be indicated in the following claims.

The accompanying drawing, in which one of various possible embodiments of the invention is illustrated, is a longitudinal section of an electromagnetic clutch incorporating the invention.

Conventional non-magnetic clutch facings belarge excitation current: difficulty has been I 2 met by the provision of magnetic clutch facings or linings of magnetic permeability higher than that of conventional linings but lower than that of the adjacent ferrousclutch faces, such as are disclosed, for example, in the copending application of Anthony Winther, Serial No. 91,792, filed May 6, 1949, for Magnetic Clutch, now Patent No. 2,580,869, and in my copending application, Serial No. 110,211, filed'August 13, 1949 for Magnetic Clutch and Lining Therefor.- While such magnetic clutch facings have been an improvement over former constructions, they do not ordinarily have the wear-resistant or high friction characteristics of conventional non-magnetic clutch linings under severe operating conditions such as envisaged herein, and as a result their life in this class of service .may be less than the life of a corresponding conventiona1 lining. Moreover, it is'difiicult, though not impossible, to obtain a satisfactory frictional coefficient, for example .03,

while also providing the desired high magnetic permeability.

Thewear-resistant quality of a clutch facing becomes especially important where the clutch incorporates servo-action wedge operators, such as will be described below; The wedge operators desirably increase the clutch closing pressures for transmission of greater torque, but with danger of an attendant increased wearing effect on magnetic clutch linings which the present invention overcomes.

, Referring now to the drawing, there is shown a compound or double magnetic clutch of the disc type, particularly adapted for automotive transmission requiring two power input members driven from a single power source. A drive shaft, for example, the crank shaft of an automotive engine is indicated at l and hasa flange 3. The fiange 3 is bolted to a hub 5 of a driving assembly forming the driving member of the clutch. The

driving member includes end walls I and 9 and an interposed and a magnetic ring assembly or field member I I formed by welded magnetic rings I IA, I IB and I IC. The cross section of assembly II is S-shaped. The hub 5, the end walls I and 9 and the assembly I l are all rigidlysecured together. Numeral 2 indicates a conventional starter gear.

Steel clutch plates I3 and I5 are positioned on opposite sides of the pressure element II, the plates being selectively operable driven members of the compound clutch, each being the driven element of one clutch. The clutch plate I3 is spring mounted on a hub I! by vibration dampers I9 of conventional construction requiring no further description. The hub I! is splined to a driven shaft or member 2|. The other clutch plate I5 is riveted to a second hub 23. Hub 23 is splined to a quill 25 rotary around the shaft 2| and constituting a second driven member. Shaft. 2| is coaxially aligned with the drive shaft I by a pilot bearing 2? supported in the hub 5 of the driving member. The quill 25 is exteriorly journalled in a suitable bearing 4 supported in the clutch housing or frame, part of which appears at 6. A pilot bearing 3 aligns the quill in one end of a sleeve in extending from plate 9. The other end of the sleeve IE3 is supported upon a bearing I2 in housing 6.

Returning to the driving member, the S-shaped assembly I I forms two annular grooves 35 and'3'I in opposite faces 39 and M. The grooves 35 and I 3? contain annular field coils 43 and 45. The field coils are adapted to be individually excited by current introduced through brushes 4'! and 49, serving the coils through collector rings SI and 53. A circuit for each coil is completed through the metal parts of the assembly to sleeve I and through a grounding brush 55. The collector rings 5i and 53 are-supported in insulated relation on the sleeve I0 and are connected to the coils by suitable wiring'50 for the purpose.

Inasmuch as there is shown a double clutch with a common pressure element II and similar parts on each side thereof, the subsequent description of similar elements will refer only to the construction of oneclutch per se, it being understood the other clutch is the same in principle. Since it has'only different dimensions of similar parts, corresponding reference characters indicating such similar parts are primed.

On the outside of clutch plate I3 is a floating, magnetic'pressure element or ring 59 which is axially and rotatably movable relative to the assembly II.- The element 59is connected to the ring assembly of the driven member by means of an inwardly positioned resilient artificial rubber or like ring 6| and by means of outwardly positioned wedge operators 33. The resilient ring 5| is compressed within an inner rim 65 on the pressure element and-seats in'a groove 68' in the flange 5 of the ring assembly.

There are a number of wedge operators, for example, six symmetrically disposed around and adjacent the periphery of the floating pressure ring. Each comprises a hardened steel ball 69 contained by conical seating cavities TI and, I2 within hardened steel insert members I3 and I4, respectively press fitted into openings in the ring assembly end Wall I and into the back of the floating pressure ring 59. A floating retainin ring I5, having ball receiving apertures, linksthe balls of the group of wedge operators.

The ring GI resiliently drives pressure element 59 when the latteris free (clutch open) but permits 55 to lag when its rotation is resisted, as when engaging the faced disc I3 during clutch closure. By toroidal rolling or twisting action it allows for axial movement of 59 while supporting itj Whenelement 59 and plate I3 are disengaged, the conical seating cavities II and I 2 are aligned. When the element 59 is brought into engagement with plate I3, and with a-relative rotation therebetween,- a drag occurs on the floating element 59 which causes it to lag with respect to assembly II and wall I. The seating cavities H and ii are then disaligned with a resultant Servo wedging action causing the floating pressure element 59 to be forced axially toward the other pressure element II for completing clutch engagement by squeezing the sandwiched disc or plate I3.

The clutch is initially engaged by magnetic attraction of the magnetic pressure elements I I and 53. An annular recess TI is formed in the face 19 of the floating element 59 and opposite the groove 35 in the face of the assembly I I. A magnetic circuit or iron path is thus provided around the field coil 43. This carries a toroidal flux field F induced by the field coil 43 interlinking both pressure elements II and 53 (see the top of the drawing). The magnetic path between the ele ments includes the magnetic plate I3 and certain of the associated clutch facings. These are soconstructed'as to reduce the reluctance of the magnetic path. Thus ring-like facings SI of low magnetic reluctance are secured on opposite sides of the clutch plate I3 inside of the recesses 35 and TI in the pressure elements. Similar ring-like facings 83 of low magnetic reluctance are secured on opposite faces of the clutch plate outside of the recesses in the pressure elements. The outer facings 63 do not extend to the outer periphery of the disc. On the outer marginal plate portions are attached ring-like facings 85 of a conventional, Wear-resistant character such as ordinary non-magnetic clutch facing. The facings 3!, 83

and 85 are attached by riveting or by the use of clutch or brake facing cement, both of which are known for the purpose. If desired the facings may be attached to'the pressure rings, instead of the disc.

Magnetic clutch facings are disclosed in the above mentioned applications, Serial No. 91,792, now'Patent No.'2,580,869 andSerial No. 110,210.

Generally, magnetic facings comprise a tough and a Items: Parts by weight Iron powder (99.7% pure iron) ranging in size from 8 to 25 microns and substantially spherical in shape Shredded asbestosyarn fibre (short pieces to inches long) 4 Short pieces of brass wire (about .0l0'inch diameter mixed with the asbestos) 2 Barytes 3 Graphite 1 Powdered, uncured phenolic resin 10 The mixture is formed as a facing and cured with heat and pressure, preferably, though not necessarily While under the influence of a strong magnetic field which is established parallel to the expected direction of the operating magnetic field through the resulting facing. This expected direction is normal to the facing considered as a sheet. Such orientation of the granulated magnetic substance further reduces the reluctance of the facing in the desired direction. This orientation feature may be omitted. It is described more in particular in said application Serial No. 110,211.

Conventional clutch facings are well known. They generally comprise a mixture of substances adapted to withstand frictional wear and heat while also providing a smooth action and high coefficient of friction. Asbestos fibre, brass wire and a binding agent are commonly employed. Conventional facings have superior wear resistance over magnetic facings because they do not and '12 are essentially 5' include the magnetic particles, which necessarily form a substantial part of the magnetic facings. Asindicated in the'drawing, the non-magnetic wear-resistant facings 85 are appreciably thicker than the magnetic linings 8| and 83. Suitable recesses 81- and 89 are provided in the pressure elements H and 59 respectively, to accommodate the greater thickness of facings 85*and provide substantially coincident engagement'of all facings with the respective pressure elements.

' Operation of the described left-hand clutch is as follows:

The clutch ring assembly including the end walls 1 and 9, and the interposed pressure element II is driven by the drive shaft I, floating pressure element 59 being also rotated therewith. This is because 581s interconnected with the ring assembly by the supporting resilient ring 6|. With field coil 43 unexcited, there is no axial forcetending to close the elements, and they rotate with negligible frictional interaction with plate l3. The friction is insufficient to overcome the resistance of the resilient ring 6| to angular displacement of the floating element relative to the ring assembly. Therefore, the ball seating members H and 73 are essentially aligned.

When the fleld coil is excited, the floating pressure element 59 is initially drawn against outer facings SI, 83 and 85 of the clutch plate I3. This is because toroidal magnetic field F interlinks the two pressure elements, passing therebetween through the magnetic plate l3 and the magnetic facings 8| and 83 but not through facings 85 which are highly reluctant. The frictional engagement of the clutch members results in a drag by plate l3 and lag or displacement of the floating elements 59. This disaligns the ball seats 13 and i4 and a servo wedging action results which forces the floating pressure element 59 toward the other pressure element II, the interposed plate 13 being in turn driven against the axially fixed pressure element. The result is, through'the facings 8|, B3 and 85, to grip plate l3 and angularly to accelerate it. The speeds of the pressure elements ll, l3 and 59 then become synchronous, under which condition lag between the floating element andthe ring assembly ceases and no further compression occurs, its limiting value being determined by the cone angles of seats II and 12 and by the force associated. with the torque which is being transmitted.

The clutch is disengaged, by deexciting the field coil 43'. A release of the wedge operators is assured by the bias on the stressed resilient ring 8| tending to return the floating pressure element to its initial position in which pockets H aligned. Moreover, the cone angles of the seats H and 12 are such as to prevent permanent looking with the balls 68, so that elements 63 tend'automatically to release and center themselves.

After a short period of initial wear on the magnetic facings 8| and 83 the more wear-resistant non-magnetic facings 85 bear the major portion of compression occurring during clutch engagement, for example, 75 to 80 percent. The magnetic facings 8| and 83, having incipiently worn back more rapidly, are then relatively'lightly loaded, their primary purpose being to fill the gap between the plate 13 and the elements H and 59 and to provide a low reluctance path therebetween.

Continued adjustment of load to the stated conditions is assured by the process of wear or lapping under conditions of operation. The magnetic facings 8| and 83 wear relatively rapidly so that they relieve themselves of some load to the extent that the non-magnetic facings 85 are engaged and primarily loaded. Further wear is resisted by the tough-'non-magnetic facings 85. The major'portion of the driving torque is transmitted through the n'on magnetic facings, because of their greater diameter and because of their higher frictional coefficient as compared to that of the magnetic facings.

The provision of magnetic facings in the magnetic path is also advantageous becauseof their wearing character which permits self-adjustment to the most efficient thickness to fill what would otherwise be a magnetic gap. Any wear in the non-magnetic facings is accommodated by additional wear in the magnetic facings. The construction permits use of a higherqiron content in the magnetic facings than might otherwise be practical. Thus the invention broadly comprises the feature of providing a wean-resistant, high frictional-coefficient facing between clutch members over a part of a clutch face, the other part of the clutch face comprising magnetic material for providing a low reluctance magnetic circuit inter-linking the pressure elements. The servo operators 63 supply the additional axial forces which the non-magnetic facings 85 can withstand and which mere magnetic attraction could not provide without a high magneto-motive force requiring large coils and large-excitation. The wedge operators 63 are positioned substantially opposite the non-magnetic facings 85, assuring a substantially direct compressivesaction.

The above description applies also to the similar prime-indexed partson the right'side of the drawing constituting the right-hand clutch. It will be observed that the left-hand clutchsupplies power to shaft 2| whereas the right-hand clutch supplies power to the quill 25. Individual excitation of coil 45 closes the right-hand clutch by providing the toroidal flux field F" (see the upper half of the drawing). The clock direction of current flow through 0011s 43 and 45 is the same, so that according to the right-hand rule the flux vectors are in the sameclock direction as shown by the arrows on 'flelds' 'F and F. The fields F and F are both indicated in the top half of the drawing, but it will be understood that they will respectively occur only if either one or the other of the coils 43 or 45 is excited. If both coils are excited at the same time (current in the same clock direction therein as stated), then the portions of these flux fields F and F between the coils 43 and 45 cancel one another and a single loop (instead of two loops) of flux occurs, such as suggested at S in the lower half of the drawing.

Under the condition indicated at S (coils 43 and '45 excited simultaneously) both clutches are closed, the mode of closing of each being as already made clear.

In any transmission served by the clutch, it is desirable that there be no period of power skip between the time that one clutch is opened and the other is closed. It will therefore be under stood that coil 45 may be first individually excited,

providing toroidal flux field F"'-to c'lose the righthand clutch. Before coil 45 is deexcited and thus I before field F disappears,,coil'43 is excited so as "to provide the fl eld conditions shown at the bottom of the drawing. Thus both clutches are closed. Then coil 45 is deexcited,- so that only flux fleld F remains to retain the left-hand clutch closed. The right-hand clutch then opens.

ag e

When both coils 43 and t are deexcited, F, F

and S all disappear. The converse of the above.

' then the right ha'ndclutch will close and subse-'. will open; 'Ihus quently the. unmade clutch power skip is prevented 4 Whereas a' clutch is described by way of ex-n ample, it will be understood the invention has application to brakes, a brake being a form of clutch, as understood by those skilled in the. art.

lhe terms are to be understood herein as synonymous.

s In viewof the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended. that all matter contained in the abovedescription or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim;

l. A magnetic clutch comprising a rotary member, a field ring driven by said rotary member, means for exciting a toroidal flux field in said field ring, a magnetic pressure ring adapted to be interlinked by said flux field and attracted, a ring composed of resilient, material and interposed between the rotary member and, the pressure ring to support the. latter for limited axial movement and for rotary lagging movement, a driven clutch plate interposed between the field ring and the pressure ring, and a lag-operated wedge mechanism between the rotary member andthe pressure ring, whereby upon excitation of the field ring with consequent attraction of the pressure ring toward the driven plate and with resulting lag ofthepressure. ring, said mechanism will act to force the pressureringto clamp said driven plate.

2. A clutchmade according to claim 1, wherein a friction liner which is non-magnetic and relatively more wear-resistant in one part and magnetic but relatively less wear-resistant in another part is interposed between the driven, plate and the field and pressure rings respectively.

3. A clutch made according to elaiml, wherein a facing which isnon-magnetic in an outer annu lar part and magnetic in an inner annular part is interposed. between'the driven plate and the field and pressure rings respectively, andwherein the wedge mechanism is located substantially opposite said outer annular part.

4. A clutch comprising a rotary member, a field ring driven by said rotary member, annular coils in said field ring adapted when individually excited to establish about each coil respectively an individual toroidal flux field, the clock directions of exciting current in said coils being the same whereby when both coils are excited a single da fl x field. set-reunite than. he S direCtiQn, m neti measu e K p-5 1. o p i sides the fi ld rine adapte resp st el s be facings being relatively non-magnetic and inner portions. thereof: bein ubstantially magnetic for. interlinkage. by said flux fields.

6.; A clutch made according to claim 4;, wherein facings are. interposed on opposite sides of the respective driven plates, outer portions of said in erl n e b resn ciiteoes. Q S9191 iedividual o a fi lds; and we a be int flieksd by i Single oidal flu ie d east driy n. plei e s iv y loca ed be w en respective sees said s r -s. nd'tbefiel e w 5. A clutch made accoi ding to claim 4 wherein facings are interposed on opposite sides of. the re e ti d en lat s Quiet Pe o of sa I Number Country Date 174,052- France Feb. 15,1915 7 556,182 England Sept. 23, 1943 599,540 England Mai. 15, 19.48

iacings being substantially non-magnetic and inner. portions thereof being substantially magnetic for interlinkage' by said flux fields, and wherein the pressure rings are supported with respect to said rotary member by annular resiliv ent rings of circular. cross section allowing limited axial and lagging movements of said pressure rings, and wherein lag-operated wedge. servo mechanisms are respectively interposed between the pressure rings and said rotary member, said mechanisms being in a position toapply thrust primarily through said outer substantially non-f magnetic facings.

'7. A magnetic clutch comp-rising a irame, a rotary driving member axially fixed with respect to the frame, a driving field ring connected with said rotary member. and also: axially fixed with respect to the frame, means for exciting a toroi dal flux field in said field ring, a magnetic pressure ring adapted to be interlinked by said fiux field and to be attracted toward the field ring, said pressure ring, being supported on the, rotary driving member for axial movement with respect to the. frame and for rotary lagging movement with respect. to. the rotary driving member, a magnetic driven clutch. plate which is axially movable with respect, to the field ring interposed between the field ring and the pressurev ring, an outer non-magnetic relatively greater wearresisting annular liner and an inner magnetic rel: atively less weariresisting annular liner, both liners being interposed between the. driven plate and the field and pressure rings respectively, the flux field of the field ring passing substantially only through the. inner liner, and a lag-operated wedgemechanism operative between the rotary member and the pressure ring and located sub-. stantially opposite said outer liner, whereby, upon excitation of the field. ring with consequent attraction of the pressure ring toward the clutch plate and with resulting lag of the pressure. ring, said mechanism will act to force the pressure ring to force said driven plate against the field ring.

MARJIIN P. WINTHE R,

REFERENCES CITED The following references are of record in the file of this patent:

2 4 7, 22 Lambert l s e t, 3, 945

FoRnIoN PATENTS 

